1. Field of the Invention
Many marine vessels, especially large ships, have deck boxes mounted within openings in the deck of the vessel. The deck box is closed by a removable cover, and the mounting is such that the covered box is substantially flush with the surface of the deck.
Removal of the cover provides access to mechanism within the deck box for operating otherwise inaccessible devices located throughout the ship. Most commonly, these devices are valves for controlling flow of liquids into and out of tanks carried by the ship.
2. Description of Prior Art
An example of a conventional deck box is illustrated and described in U.S. Pat. No. 4,655,160. Typically, the deck box includes a cylindrical housing permanently secured within an opening in the deck, such as by welding or bolting. The housing is provided with an internal screw thread which cooperates with an external screw thread formed in the deck box cover. Thus, the deck box is closed by screwing the cover into the housing as far as possible, and opened by unscrewing the cover from the housing.
Use of screw threads on the cover and housing present a number of problems. Although the cover fits reasonably tightly in the housing, nevertheless grit and other foreign matter, such as wax, find their way into and between the screw threads making the cover difficult to open and close. This necessitates time being spent cleaning the screw threads, which still does not completely eliminate the problem. In addition, because, over time, the cover becomes difficult to screw into the housing, it is sometimes difficult to know whether or not the cover has been screwed all the way into the housing as far as it will go. This is important, since inserting the cover to its maximum depth insures that the O-ring, provided between the cover and shell, is squeezed tightly to make the closure water-tight. Moreover, screwing and unscrewing the cover is relatively time consuming, which can present a problem when quick access to a valve is required.
It is an object of the present invention to overcome these problems by eliminating the screw thread connection between the cover and housing, and thereby eliminating the problems attendant to use of screw threads.